Difference 2.0 DOHC 85/88 KW ???

Hello guys, I’ve finally been Sierra driver for a few days. By stupid coincidence I bought two pieces now. On the one hand a 89er Sierra Combi with 88 KW and on the other hand the 92er 3-door FLH with 85 KW long sought by me. At the “transmission” of the two cars I noticed that the combi runs at Tempo 100 in the 5th gear only scarce 2000 rpm and the FLH already at 3000 rpm. As far as I could research this up to now, the two 2.0 DOHC are identical, only the newer ones have some reduction piece and thus a little less power. Why actually? Are there still different gears? Last question: Is it now the 2.0 DOHC or the 2.0i DOHC??? Motor codes should be N9C (Kombi) and N9E (FLH). Thank you already, look forward to your answers, f-b